Sensitizing photographic emulsion



` the dlsubstitution products Y Re standsfor alkyl,

Patented Aug, 9, 1938 PATENT .orElcE 2,126,078 sENsrrIzlNG Pno'rocnsrmo EMULsIoN l Walter Zeh,

, Frank! Dessau in Anhalt. Adolf Siegllta, rt-on-thc-Maln-Sindlingen, `and Martin Dabelow, Frankfort-on-the-Main-Hochst,

Germany, asslgnors to Agfa Ansco Corporatiominghamton, N. Y., a corporation o! New York Application February 28, 1935, Serial No.' 8,658 In Germany April 26, 1932 2 Claims.

Our present invention relates to sensitizins f photographic emulsion. It is a continuation in part oi our co-pending application Ser. No. 667,712,nled April 24, 1933.

One of its objects is to provide such an emul` sion the sensitivity of which is raised over the range of wave length's to which the emulsion is normally sensitive. Another object are the dyes incorporated in the emulsionin order to increase its sensitiveness. Further objects will be seen from the detailed specification following here` after. Reference is made to the accompanying drawing which shows the spectrograms 0I an unsensitlzed emulsion and differently sensitized emulsions.

It is already known to sensitlze silver halide ,emulsions by means of trimethinecyan'ines which are substituted in the benzene nucleus. These dyes when suitably selecting vthe substituents distinguish over the non-substituted dyes by an increased sensitizing power.

This invention ls based on the discovery that nines of which the iii-positions of the benzene nucleus are occupied by equal or dissimilar substituents are far superior to all other substituted dyestuils. 4It has proved that these dyes substituted in the 5 and 6 positions are superior with regard to their sensitizing action to those substituted, for instance, in the 5 or 6 position orY to the disubstituted dyes when containing theV substituents in other positions or the benzene nucleus or even to trisubstituted dyes.

The dyestufi's suitable for the present process are derived from the following formulae:

.n.rn.; 4 l lil I i Y and Z stand for lS, Se, or

wherein Rf and R," may be alkyl or aryl., R1. Rn, R.: and R4 stand for alkyl, alkoxy, thioalkyl, selenoalkyl, aryl or aryloxy,

Rn stands for hydrogen,

alkyl, aryl, aralkyl or thienyl, and 1 of the trimethinecyation of trimethinecyanines in 5- x swnds'mr c1, Br,1, soicna. Clo. or another acid radical.

alkyl, aryl, aralkyl or AI, SOlCI-Ia, C104 or another Y and Z i'cr S, Be,or

RII

Furthermore the hydrogen atoms of the lateral 1. soicr'n, cio. or another members oi the polymethinechalns may be subl stituted by similar or dissimilar alkyl groups.

Instead or two alkoxygrcups f or the substituvand 6positions, there may be used a dioxymethylene group or a dioxyethylene group. In the same way two aryloxy groups may phenylene group. A

In the accompanying drawing there are reprobe replaced by a dloiry duced four spectrograms of the same silver bromide gelatin emulsion containing about 4 per cent of silver iodide.

Fig. 1 shows the spectrogram of the unsensitized emulsion,

Fig. 2 shows the spectrogram of the emulsion sensitized with bis-[3-ethyl5.6dimethoxybenz thiazole- (2) l-trimethine-cyanine bromide,

Fig. 3 shows the spectrogram of the emulsion sensitized with bis-i3ethyl4.6.7trimethoxy benzthiazole- (2) l-trimethinecyanine bromide,

Fig. 4 shows the spectrogram of the emulsion sensitized with bis-[3-ethyl4.7-dimethoxy-benzthiazole- (2) l-trimethinecyanine iodide.

In the spectrograms the abscissae are graduated in millimicrons (an) while the ordinates are graduated in divisions denoting the blackening of the tested lm. The blackenings are taken -by exposing the film in a diffraction grating spectrograph of Carl Zeiss. Jena, provided with a Rowland diffraction grating, and illuminating with a nitra lamp of.100 watts through a stage slot. The stage slot has 6 stages and exposure is thus effected that the 6th stage is just visible in the standard sensitiveness of the emulsion or in the range of sensitiveness imparted to the emulsion by the sensitizer.

The dyes are obtainable according to the dey sired solubility in form of the bromide, iodide, perchlorate etc. and are used in a quantity as usual for the known sensitizing dyes. 'I'hls quantity amounts to about 10 to 30 milligrams per 1 kg. of emulsion ready for being cast which contains about 9 per cent of gelatin, 4.5 per cent of silver-halide, the rest being water. However, we do not wish to limit our invention to the quantities just indicated, the most suitable .amount will in each case be found by a few comparative experiments. Thedyes maybe added to the emulsion in form of solutions. Suitable solvents are lthe alcohols, for instance, methyl or ethyl alcohol of methanol of 50 per cent strength for about 5 minutes. The material is then dried, whereupon it is ready for use. i

The preparation of the dyes and the bases from which the dyes are prepared is analogous to known methods.

1. The preparation of 5.6-dimethoxy-2-methylbenzthiazole is described by Fries in Annalen der Chemie, vol. 488, 1929, pages 170 and 171.

2. 'I'he bases 5.6-diethoxy-2-methylbenzthiazole and 5.6methylenedioxy2-methylbenzthiazoley are prepared according to the same method by starting from the corresponding amines.

3. 'Ihe base 2.5.6-trimethylbenzthiazole is prepared analogously to known methods in the following way:

(b) 'I'he thiourea is'transformed into 2-amino- 5.6-dimethylbenzthiazole bymeans of sulfurylchloride. i

(c) The aminothiazole is made into 1amino 2-mercapto4.5-dimethylbenzene by means of potassium hydroxide under pressure.

(d) 'I'he aminomercaptane yields the 2.5.6-trimethylbenzthiazole when treated with acetic anhydride.

4. The preparation of 2-methyl-5-methoxy-6- meth-thiobenzthiazole is as follows:

(a) By the reaction on l-chloro-2-methoxy-4- nitrobenzene with sodium disulde the di-(2- methoxy4-nitrophenyl) -disulflde is formed.

y (b) 'I'he disulde is dissolved in sodium hydrosulflde and methylated by means of dimethylsulfate. There is obtained l-meth-thio-2-methoxy- 4-nitrobenzene.

(c) 'I'he nitro product is reduced to l-meththio2-methoxy-4-amino-benzene.

(d) The amino compound is made into the thiazole according to the method described by Fries above referred to.

5. The 2.5-dimethyl--ethoxybenzthiazole and 2.5-dimethyl-6-ethoxybenzothiazole are obtainable according to the method disclosed by Fries above referred to from 3-ethoxy-4-methyl-laminobenzene and 3-methyl-4-ethoxy-l-aminobenzene respectively.

'I'he preparation of the seleno-azole bases is eiected according to the method disclosed in "Berichte der Deutschen Chemischen Gesellschaft", vol. 46, 1913, pages 92 to 97, by starting from 4.5 disubstituted o-nitroanilines corresponding with the general formula R NH:

illustrate our HICO S S OCB:

, a n H may be obtained by heating 10 grams of 2- methyl-5.6-dimethoxybenzothiazole and 10 grams of p-toluene sulfonic acid ethyl ester -for 3 hours to 130 C. After cooling the mixture 100 cc. of dry pyridine and grams of triethyl-o-formate are added and the mixture is heatedK for 2 hours under redux. After removing the pyridine by distillation in the vacuum the residue is dissolved in 250 cc. of alcohol and to the solution there is added aconcentrated aqueous solution of 4.1 grams of'potassium iodide. The dye crystallizes in the form of green rods and is recrystallized from alcohol.

'I'he alcoholic solution of the dye has an absorption maximum at a wave length of about 595ML.

Incorporated in a gelatino silver bromide emulsion containing about 4 per cent of silver iodide. the dye imparts to it a range of sensitiveness from about 500ml to 710W with a maximum at about 825ML.

methyl-5.Gf-methylenedioxybenzthiazole with 10 sorption maximum at a wave los 22:2@ utilizzi:

may be obtained by heating 12 grams o! 2-methy1- 5.6-diethoxybenzthiazole with 10 grams of ptoiuene sulfcnic acid,A ethyl-ester for 3 hours to 130 C. After cooling there areadded 120 cc. 'of dry pyridine and 15 grams ottriethyl o-tormate and the mixture is boiled for 2 hours under reiiux. The further working up of the dye is as described in Example 1. The dye crystallizes fromlalco'hol in the form of green rods.

The alcoholic solution of the dye has an absorption maximum at a wavelength of about 800;1.;L.`

incorporated in a gelatine silver bromide emulsion containing about 4 per cent of silver iodide, the dye imparts toit a range of sensitiveness from about 500aato about 710ml. with a maximum at about 630ml which is fiat.

Example 3.-The dye bis-[3ethyl-5.6methyl enedioxy benzthiazole (2) l-trimethinecyaninebromide correspondingwith the formula En nel 1 CsHn Bi' may be obtained by heating 9.6 grams of 2- O Lila grams of p-toluene sulionic acid ethylester' for about 3 hours to 130 C. After cooling there are added 120 cc. of dry pyridine and 15 grams of triethyl o-i'ormate whereupon the mixture is boiled for about 2` hours under reux. The further working upc! the 'dye is as described in Ex ample 1. The dye crystallizes from alcohol in green rhombic crystals.'

The alcoholic solution of the dye has an ablength of about Incorporated in a gelatino silver bromide emul.. sion containing about 4 per cent oi silver iodide. the dye imparts to it a range or sensitiveness from about 500ML to '110W 'with a maximum at about 640ml..

Eample 4.- The dye bis-[3-ethyl6.6di methyl-benzthiazole(2)l p-methyl-trimethinecyanine iodide corresponding with the formula 21pm 11h11- J obtained in the formo! green tetrahedral cryst n als. n

The alcoholic solution of the dye has an abl sorption maximum at a wave length ot about 555ml. v

Incorporated in a gelatino silver bromide emulsion containing about 4 per cent of silver iodide, the dye' imparts to it. a range ci sensitiveness from about 500ml to 680ml with a maximum at about 600ml which is very at.

Example 5.-The dye bis- [3-ethyl-5-dimethoxy benzthiazole- (2) l ethyltrimethinecyanine iodide corresponding with ,the formula l is obtained when working as described in Ex# ample 1 but using triethyl o-propionate instead .of triethyl o-Iormate. The dye crystaliizes from about 490m; to 690ML with a maximum at about 600ML which is very dat.

Example 6.--The dye vbis-[ii-ethyl-b-diethoxy benzthiazole (2) l--methyl-trimethinecyanine iodide corresponding with the formula C1B; I 41H1 is obtained when working asdescribed in Example 2, but using triethyl o-acetate instead of `triethyl o-iormate. The dye crystallizes from alcohol in the form of bluish violet rods.

The' alcoholic solution ot the dye has an ab sorption maximum at a. wave length of about 585ml.

Incorporated in a gelatino silver bromide emulsion containing about 4 per cent of silver iodide. the dye imparts to it a range of sensitiveness from about 490ml to 690ML with a maximum at about 805ml which is very flat.

Example V7.-'Ihe dye bis-[B-ethyl-B-dimethoxy-benzselenazole-(il) l trimethinecyanin iodide corresponding with the formula moo dimethylbenzselenazole diethylsulfate. v(prepared by heating 10 grams of 2methyl5.6dimethoxy benzselenazole with 6 cc. of dieth'ylsulfate for 3- hours to 100 C. and purifying the reaction product by washing with acetone) 10 cc. o! pyridine and grams oi triethyl o-iormate'ior about 1. hour to 130 C. On the addition of about 30 cc. of an aqueous solution or potassium bromide oi per cent strength the dye separates in the form o! blue flakes. Recrystallization from alcohol yields greenish blue relted needles.

The alcoholic solution ot the dye has an abis obtained by heating 5 grams of S-methyl-S- sorption maximum at a -wave length of about 610ml.

Incorporated in a gelatino silver bromide emulsion containing about 4 per cent of silver iodide, the dye imparts to it a'range of sensitiveness from about 500ML to 730ml with a maximum at abllt 650ml..

Example- 8.-The dye bis-[3-ethy1-5-6-diethoxy benzselenazole (2) l trimethinecyaniney bromide corresponding with the formula Se Se OCzI-I;

H H Il N/laalztm.

Cans I Cans is obtained when working according to Example HiCzO- 7, but starting from 2-methyl-5.6diethoxybenz l selenazole diethylsulfate. The dye crystallizes from alcohol in the form of blue little rods.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 610ml..

Incorporated in a gelatino silverfbromide emulsion containing about 4 per cent of silver,

iodide, uthe dye imparts to it a range of sensitiveness from about A500ml to 730W with a maximum at abOlIt 650ml..

Example 9.-The dye bis-[3-ethyl5.6ethyl enedioxy benzselenazole- (2) ltrimethinecyanine iodide corresponding with the formula is obtained when condensing 2-methyl-5.6ethyl enedioxybenzselenazole diethylsulfate with triethyl o-formate and precipitating the dye with an aqueous solution of potassium idodide, of

is obtained when Working according to Example 9, but using triethyl o-propionate instead of tri-y ethyl o-formate. N

'I'he alcoholic solution of the dye has an absorption maximum at a wave length of about 590ML.

Incorporated in a gelatino silver bromide emul sion containing about 4 per cent of silver-iodide, the dye imparts to it a range of sensitiveness, from aboutf490aa to '110W with a maximum at about 620ml..

inecyanine perchlorate corresponding with the formula Cans C104 01H5 is obtained by boiling 5 grams oi 2-methyl- 5.6-dimethoxybenzselenazole diethylsulfate and '5 grams of triethyl o-propionatc in 10 cc.

of dry pyridine under reiux for about 1 hour. On the addition o1' 30 ce. of an aqueous solution of sodium perchlorate of per cent strength the dye separates. Recrystallization from alcohol yields blue needles.

The alcoholic solution of the dye has an absorption 'maximum at a wave length of about 595ml. y

Incorporated in a gelatino silver bromide emulsion containing about 4 per cent of silver iodide, the dye imparts to it a range of sensitiveness from about 490ml to 710W. with a maximum at about 610ml. i

Example 12.The dye bis-[3-ethyl-5.6dl methyl-benzthiazole-(2) l =-ethyltrimethinecy anine iodide corresponding with the formula HzC CH;

the dye imparts to it a range of sensitiveness from about 500ML to 650ml with a about 600ml.

Example 13.-The dye bis-[3-ethyl-5-phenyl-6- methoxy benzthiazole (2)] trimethinecyanine bromide corresponding with the formula ii-ii; CEs Br 1HE is obtained by heating 12.7 grams of 2-methyl-5- phenyl-6-methoxybenzthiazole with 10 grams of p-toluene sulfonic acid ethylester for 3 hours to 130 C. and condensing the reaction product with grams of triethyl o-formate in 120 cc. of pyridine and further working up the product in the manner described in Example 1 withthe ex' ception that the dye is precipitated by means oi about cc.of an aqueous solution of potassium bromide of 20 per cent strength. The dye crystallizes from alcohol in the form of little green rods.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 585ml.

Incorporated in a gelatino silver bromide emulmaximum at HICQ OCB CaH 06H5 .sion contaix 'ng about 4 per cent of silver iodide,

the dye imparts to it a range-of sensitiveness from about 500W. to 700W. with a maximum at about 620.

' ethyl-trimethineoyanine sion containing about 4 hours to 130 to 140 Aaction mixt andere Example 14.-'rne dye sis-[s-ethyl-s-methoxy- G-methylthiobenzthiazole (2)] 'trimethinecyanine bromide corresponding with the formula4 mos s s son a H H moo Lof-(IJQOCH. N/ N Cabs. .H.

is obtained when working according to Example 12, but starting from'llfl grams of 2-methy1-5- methoxy-5-meth-thiobenzthiazole and 10 grams of p-toluene sulfonic acid ethylester. The dye crystallizes from alcohol in the form of bluish i green felted needles.

The alcoholic solution of the dye has an absorption'maximum at a wave length of .about Incorporated in a gelatino silver bromide emulper cent of silver iodide, the dye imparts to it'a range of sensitiveness from about 510ML to '120ml with a maximum -at about 640W which is very flat.

Example 15.-*4-The dye bis-[1.3.6-tetramethyl- 5-chloro -indole- (2) l-trimethinecyanine chloride corresponding with the formula CH; CH CH:

CH: v

4is obtained when working in the manner described in the example of- U. S. Patent 14524,'191 and starting from 1.3.B15-methyl-6-chloro-2- methylene-indoline.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 560/141.:

Incorporated 'in a gelatino silver bromide emulsion containingv about 4 per cent of silver iodide, the dye imparts to it a range of sensitiveness of about 500Ml`to 630ML with a maximum at about Example 16.-The dye [ii-ethyl-benzselenazole- (2) [3-ethyl-5.6 dimethylbenzthiazole-(2H-piodlde corresponding with the formula y l Gi/HI\ I is obtained as follows: l

(a) grams of 2-methylbenzselenazole ethiodide and 9` cc. of ethylisothiopropionanilide are heated to about 165 to 1'10l for about 1% hours while repeatedly stirring. 'Ihere is pro' duced a homogeneous melt of dark color which is dissolved in cc. of alcohol. This solution ls mixed with about cc. of ether while stirring. The intermediate product which crystallizes is vitered and reorystallized from alcohol.

i (b) 5 grams of this intermediate product, 5 grams of 2.5.6-trimethylbenzthiazole ethiodide and 10 ce. of pyridine areheated for about 11/2 C. so that nally there is evaporated about half of the pyridine quantity employed. Hereafter there are added to the rea few cc. of anaqueous solution ofpotas and a small amountof water.

. After cooling the with the formula about 500ml to 690mm4 with a maximum ium iodide of 10 per cent strength dye separates.l The dye may be puried by recrystallization from alcohol.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 565ML.

Incorporated in a gelatino silver bromide emul sion containing about 4 per cent of silver iodide,

the dye imparts to it a range ofI sensitiveness of labout 500,41. to 700ML with a. maximum at about n l o om. .m

is obtained as follows:

(a) 'A mixture of 10 grams of Z-m'ethylbenzthiazole ethiodide 7 grams of ethylisothio-acetanilide and cc. of acetic anhydride are boiled for about 4 hours under reflux. After cooling and the addition of much ether a thickly liquid brown mass separates. The ether is decanted and the mass is further washed two times with ether by decanting. The residue is dissolved in about 12 cc. of alcohol at a temperature of aboutv 50 to 60 C. After cooling the intermediate product corresponding probably with the formula separates in the form of crystals.

(b) 3 grams of this intermediate product, 3 gramsof 2.5.6-trimethylbenzthiazole ethiodide and 12 cc. of pyridine are boiled for 1% hours. The dye is precipitated by the addition of a few cc. of an aqueous solution of potassium iodide of 10 per cent strength and is recrystallized from alcohol.

The alcoholic solution of the dye has an absorption maximum at a wave length of about 555ML y l Incorporated in a gelatino silver bromide emulsion containing-about 4 per cent of silver iodide, the dye imparts to it a range of sensitiveness of sponding with the formula Si CHI N .O 01H; I 31H1 E ClHl H @niet is obtained by boiling 6 Vgrams of the intermediate product described in Example 16, 6 grams of 5-ethoxy- 2-dimethylbenzthiazole ethiodide at about col and 18 ccbof pyridine and working up the reaction mixture as described sub; (b) in Example 16.

The dye may be purified by recrystallization from alcohol. s

The alcoholic solution of the dye has an ab'- o'iption maxim um at a wave length of about Hl'.

6 :,laoms Incorporated in a gelatino silver bromide emulsion containing about 4 percent of silver iodide, the dye imparts to it a range oisensitiveness of about 505ML to 705W. with a maximum at about 655ML.

Example 19.-'Ihe dye [3-ethyl-5-methoxybenzselenazole=(2) l [3-ethyl-5-6-dimethyl-benzthiazole- (2) ]ethyltrimethinecyanine perchlorate corresponding with the formula is obtained by boiling 10 grams of the intermediate product produced as described in Example 16, by starting from 2-methyl-5-methoxybenzselenazole ethiodide, 10 grams of 2.5.6-trimethylbenzthiazole ethiodide and 30 cc. of pyridine for about 1 hour to 130 C. The dye is precipitated from its solution in pyridine bythe addition of 5 cc.'of an aqueous solution oi' sodium perchlorate of 10 per cent strength. Recrystalllzation from alcohol yields bluish green ielted crystals.

'Ihe alcoholic solution oi' the dye has an absorption maximum at a wave length of about 575ml.

Incorporated in a gelatina silver bromide emul.. sion containing about 4 'per cent of silver iodide, the dye imparts to it a range oi. sensitiveness of about 500ml to 710ml with a maximum at about 6651441.

It is to be understood that our invention is not limited to 'the foregoing examples or to the specific detalls given therein. Numerous other embodiments are possible and we contemplate as included within our invention all such modifications and equivalents as iall within the scope oi' the appended claims. The nomenclature used is familiar to every chemist skilled in the art and has the advantage of clearness. The formulae of the dyes as given herein represent the molecular structure of our new dyes so far as known. If, however, in future it should become evident that the formulae do not exactly correspond to the dyes, this fact will not aiect our invention since the dyes will be easily identiiied by the method o1' producing the same which has been fully described in the examples and is analogous to known methods.

What we claim is:

1. A photographic material comprising a silver halide emulsion containing a dye corresponding with the formula wherein 2. A photographic material comprising a silver halide emulsion containing y bis- [3ethyl-5.6di methoxy-benzthiazole (2)] trimethinecyanine iodide.

WALTER ZEH. ADOLF SIEGHTZ. LIARTIN DABELOW. 

